1. Field of the Invention
The present invention relates to an internal combustion engine equipped with an electronic control unit (ECU) or an electronic engine control module (ECM), and specifically to an electronic engine control apparatus for electronically controlling switching between an homogeneous combustion mode and a stratified combustion mode, and being capable of make a torque correction depending on engine/vehicle operating conditions.
2. Description of the Prior Art
It is a conventional practice to realize a desired torque, for example during shifting operation of an automatic transmission, utilizing feed-back control for an intake-air flow rate so that the actual engine output torque is converged to a desired torque. At the same time, a spark-timing correction is executed on the basis of the deviation between the actual engine torque and the desired torque value. Generally, the responsiveness of an electronic spark-timing control is faster than that of the electronic intake-air flow rate control. One such electronic engine control apparatus has been disclosed in Japanese Patent Provisional Publication No. 5-163996. On the other hand, recently, there have been proposed and developed various in-cylinder direct-injection spark-ignition engines in which fuel is injected directly into the engine cylinder. Generally, on such direct-ignition spark-ignition engines, a combustion mode is switchable between a homogeneous combustion mode and a stratified combustion mode, depending on engine/vehicle operating conditions, such as engine speed and load. In more detail, the direct-injection spark-ignition engine uses at least two combustion modes, namely an early injection combustion mode (i.e., a homogeneous combustion mode) where fuel-injection early in the intake stroke produces a homogeneous air-fuel mixture diffused adequately in the combustion chamber, and a late injection combustion mode (or a stratified combustion mode) where late fuel-injection delays the event until the end of the compression stroke to produce a stratified air-fuel mixture and to carry the mixture layer to the vicinity of the spark plug.